Apparatus and method of producing a sensing substrate

ABSTRACT

An occupant or object sensing system in a vehicle includes electrical circuits for capacitive sensing and corresponding circuits shielding the sensing system from interference. A sensing circuit and a shielding circuit may be printed by screen printing with conductive ink on opposite sides of a non-conductive substrate. The substrate is a plastic film or other fabric that has an elastic memory structure that is resilient to stretching. The conductive inks used to print circuits onto the substrate have a similar resilience to stretching such that the substrate and the circuits thereon can be subject to deforming forces without breaking the printed circuits. The substrate may be covered with a carbon polymer layer to provide alternative conductive paths that enable fast recovery for conduction in the presence of any break in the printed conductive traces on the substrate.

BACKGROUND

Current implementations of capacitive sensing technologies are oftenconfigured for placing around automobile steering wheels or possibly forpositioning within a vehicle seat so that conductive objects, like ahuman body, can induce electrical responses in the sensing systems thatare useful for occupant detection. In earlier embodiments, a system forutilizing capacitive sensing techniques may include a sensor mat havingan electrical circuit thereon that detects the presence of one or moreparts of a human body or other object in proximity to the sensor mat. Inthese installations, the sensor mat is often disposed between an outersection of a steering wheel and a rim of a steering wheel frame. Thesteering wheel frame is typically made of metal, such as a magnesiumalloy or steel, and can be a source of interference (e.g., withoutlimitation, parasitic capacitance and/or undesirable electromagneticresponses) that distort the electrical signal(s) in the sensor mat. Inother installations, a vehicle seat may include a capacitive sensingsystem that is near a similar metal infrastructure that can interferewith capacitive sensing operations that are useful for occupantdetection systems.

Traditional capacitive sensors and their associated shielding systemsare often layered assemblies that include a sensor mat, a shieldinglayer, and/or a heating mat that collectively allow for physicaldetection of an occupant's body, an occupant's position in a vehicle, orplacement of an object in a vehicle. Generally, in prior embodiments, apower source provides a voltage signal to a shield mat to provideelectrical shielding for a sensor mat. Interference with the electricalsignal(s) carried by the sensor mat may occur due to the proximity ofthe sensor mat to a metal object such as a steering wheel or seat frame,and providing the shielding voltage signal to the shield mat preventsthis interference. In addition, the system may also include a heatermat. The heater mat may be separate from the shield mat or it may beused as a combination heater and shielding mat. To use the heater mat asa shield mat, the power source generates a heating current for heatingthe steering wheel or the shielding voltage signal for using the heatermat as a shield mat. The heating current is greater than a shieldingcurrent.

Problems arise, however, when layered assemblies are too thick or bulkyfor installing in conjunction with various components of a vehicle, orthe materials used in the layers are not amenable to forming into adesirable shape for a given application. Accordingly, there is a need inthe art for improved systems and methods for making a capacitive sensorsystem, that includes an associated shielding apparatus, such that thesensor and shield can be placed in more diverse areas of a vehicle body.Of course, all improvements to the structures of a capacitive sensingsystem must still reliably provide changes in electrical outputs thatcan be used for numerous occupant detection and occupant safetypurposes.

BRIEF SUMMARY

Systems and methods of shielding a sensor system in a vehicle aredisclosed herein.

In one embodiment, a substrate includes a non-conductive sheet having afirst face and a second face with respective conductive traces adheredto the first face and the second face. The sheet and the traces eachcomprise flexible compositions with mutual resilience to stretch andcontract in conjunction with one another. The resilience maintainsstructural continuity of the conductive traces in the presence ofdeforming forces upon the sheet.

In a different embodiment, a substrate includes a non-conductive basematerial having a first face and a second face with respectiveconductive traces adhered onto the first face and the second face. Thebase material and the traces each have flexible compositions with amutual resilience allowing the base material and the conductive tracesto stretch and contract in conjunction with one another and maintainelectrical continuity of the conductive traces in the presence ofdeforming forces upon the substrate. This embodiment may further includea first carbon polymer layer connected to the first face of thesubstrate and a second carbon polymer layer connected to the second faceof the substrate.

In another embodiment, the carbon polymer layers extend over and betweenthe conductive traces for additional redundancy in electricalconductivity.

A method of printing the conductive traces on the substrate is alsodisclosed below.

BRIEF DESCRIPTION OF THE DRAWINGS

The components in the drawings are not necessarily to scale relative toeach other. Like reference numerals designate corresponding partsthroughout the several views.

FIG. 1 illustrates an exploded view of layers in a sensor mat accordingto one implementation.

FIG. 2 illustrates a front plan view of an assembled sensor mat layeraccording to the implementation in FIG. 1.

FIG. 3 illustrates a perspective view of a first example circuit patternprinted onto a sensor mat according to one implementation.

FIG. 4 illustrates a perspective view of a second example circuitpattern printed onto a sensor mat according to one implementation.

FIG. 5 illustrates a schematic diagram of a steering wheel systemutilizing a sensor mat having printed circuits thereon according to theembodiments herein.

FIG. 6 illustrates a schematic diagram of a steering wheel system usingthe sensor mat according the embodiments herein with a heater mataccording to another implementation.

FIG. 7 illustrates a top view of a sensor mat as disclosed herein,showing a schematic area of sensing zones and selected sensor returnwires from each loop associated with each zone.

FIG. 8 illustrates a top view of a sensor mat as disclosed herein,showing a schematic area of sensing zones and a different set ofselected sensor return wires from each loop associated with each zone.

FIG. 9 illustrates a top view of a sensor mat as disclosed herein,showing a schematic area of sensing zones and a different set ofselected sensor return wires from selected circuits associated with eachzone.

FIG. 10 illustrates a top view of a sensor mat as disclosed herein,showing a schematic area of sensing zones and a different set ofselected sensor return wires from selected circuits associated with eachzone.

FIG. 11 illustrates a top view of a sensor mat as disclosed herein,showing a schematic area of sensing zones and a different set ofselected sensor return wires from selected circuits associated with eachzone.

FIG. 12 illustrates a schematic view of a computer environment in whichembodiments of this disclosure are implemented.

DETAILED DESCRIPTION

Apparatuses, systems and methods of electronically sensing occupants andother objects within a vehicle, along with appropriate shieldingmechanisms to account for electrical interference, are disclosed herein.Certain examples of capacitive sensing apparatuses are explained in thecontext of a hand placement detection system that is particularly usefulfor steering wheel applications, but such descriptions are not limitingof this disclosure. The concepts described herein are equally applicableto occupant and object sensing technologies that can be placed within orproximate to any vehicle component that would benefit from electronicsensing, associated shielding functions, and computerized analysistechniques that provide control data to vehicle data management systems.Terms used in this disclosure, therefore, are intended to imply theirbroadest meaning. For example, references to “vehicles” include allforms of transportation apparatuses in which occupants move from onedestination to another. In fact, certain physical implementations of asensing system may be useful in numerous kinds of electronic sensingenvironments, and the term “capacitive” sensing is not intended to bethe sole technology sector that can utilize the structures describedbelow.

One non-limiting implementation of capacitive sensing technologies is asensor system that includes a substrate 190 configured for placement inor on multiple structures within the interior of a vehicle. Asillustrated in FIG. 1, a substrate 190 may include a base material,layer or sheet 100 that allows for constructing both a sensor circuit124A, 124B, 124C and a shield circuit 122 thereon with a minimal numberof layers. In fact, by utilizing printing operations and conductive inkproducts, both the sensor circuits 124A, 124B, 124C and the shieldcircuits 122 can be formed on opposite sides 110, 120 of a single layer(i.e., a single mat) 100. In this embodiment, a substrate 190 forplacing in a sensing system within a vehicle includes a non-conductivesheet 100 having a first face 110 and a second face 120. Respectiveconductive traces 122, 124A-C are printed onto and adhered to the firstface and the second face of the sheet. In one embodiment describedbelow, the conductive traces may be screen printed onto the oppositefaces 110, 120 of the substrate in a silver polymer ink as illustratedin FIG. 1. In non-limiting examples, the sheet 100 may be a thin nylonfabric that is between 0.10 mm and 0.2 mm thick. The conductive tracesdescribed herein may be between 0.10 mm and 0.15 mm thick.

One non-limiting goal of the described embodiments is to provide asensing and shielding structure that can be positioned withinhard-to-fit vehicle components of numerous shapes, contours, and sizesinside a vehicle. To accomplish this goal, the sheet 100 and the traces122, 124A-C each comprise flexible compositions with a mutual resiliencethat allows the substrate and the traces to stretch and contract inconjunction with one another. The term mutual resilience is intended fordescriptive purposes only, but in general, the resilience of thenon-conductive sheet 100 and the electrically conductive traces 122,124A-C is coordinated to maintain structural and electrical continuityof the conductive traces in the presence of deforming forces upon thesheet. The sheet 100 and the conductive traces 122, 124A-C are designedwith stretching parameters that overlap so that deforming forces cannotstretch or contract the overall substrate 190 in a manner that breaksstretching limits for either or both of the sheet 100 and the conductivetraces 122, 124A-C thereon. In other words, the sheet can be molded,shaped, folded, and most importantly, stretched to comply with designconsiderations without breaking the circuits formed by the conductivetraces. The sheet and the conductive traces are configured to withstanddeforming forces that stretch a dimension of the sheet in any directionby an amount between 2 percent and 10 percent. FIGS. 3 and 4 illustratethat conductive traces 122, 124A-C on opposite sides of the sheet 100,as well as the sheet itself, can have length and width dimensions alongaxes A-A and B-B. Accordingly, the mutual resilience between thenon-conductive sheet 100 and the respective traces 122, 124A-C onopposite sides 110, 120 of the sheet give the substrate 190 a memoryshape effect, allowing the entire substrate 190 to be subject tostretching, contracting, or other deforming forces along the axeswithout breaking the conductive traces and the resulting shielding andsensing circuits.

FIGS. 3 and 4 show that the conductive traces 122, 124A-C define a firstpattern 71 on the first face 110 of the non-conductive sheet 100 and asecond pattern 81 on the second face 120 of the sheet 100. In otherembodiments, the first and second patterns 71, 81 may be similar or evenidentical. In one non-limiting example, the conductive traces on theopposite faces of the sheet operate similarly to separate sensor matsand shielding mats of multi-layered capacitive sensing devices, but withmuch more flexibility in design and more possible uses that requirespace saving efficiency not seen in prior devices.

In one non-limiting embodiment, FIG. 3 illustrates one implementation ofa printed metallic mesh layer in which metallic traces 122 are printedtogether in a way that resembles a weft knit pattern and are printed ona first side of a non-conductive sheet described above to form a meshshield circuit 7. FIG. 4 illustrates how a different pattern on a secondside 120 of the non-conductive sheet 100 can form a mesh layer in whichmetallic traces 124A-C are printed to a second pattern 81. The patternsshown in FIGS. 3 and 4 allow the mesh shield circuit paths and sensorcircuit paths in the respective patterns to maintain contact whenstretched, which maintains electrical conductivity through the meshprint after the substrate 190 is secured to the steering wheel rim.These patterns are exemplary, and other suitable knit-like patterns maybe used in other implementations. The printed mesh can stretch about 2percent to about 10 percent along axis A-A or axis B-B in the presenceof about 100 N of force without interfering with the conductiveproperties of the traces, according to certain implementations. Inanother embodiment, the printed mesh and the base material sheet 100 maybe characterized as stretching about 5 percent to 8 percent for every100 N of force.

During installation of the printed mesh shield circuit 7, 122 on thesteering wheel rim, the overall substrate 190 is stretched along the A-Aaxis and the B-B axis. This arrangement of the mesh layer improvescontact between the adjacent traces to withstand such deforming forceson the substrate.

In certain implementations, the printed mesh shield circuit 7, 122 mayinclude one mesh layer area that provides one conductive zone adjacentthe base layer 100. However, in other implementations (not shown), themesh shield circuit 7, 122 may comprise a plurality of separate meshlayer areas that are spaced apart and separated from each other on thenon-conductive sheet 100 but are electrically coupled together toprovide one conductive zone adjacent each of the plurality of mesh layerareas. Such an implementation provides targeted shielding to aparticular area of the steering wheel and reduces the amount of meshlayer used for the mesh shield circuit 122. In another implementation(not shown), the plurality of separate mesh layer areas may not beelectrically coupled and are instead coupled separately to the powersource to provide separate conductive zones that can be activatedseparately. The same parallel construction is available for zones in thesensing circuits 124A, 124B, 124C.

As noted, one aspect of a substrate 190 according to this disclosure isthe ease with which the substrate 190 can be stretched for molding intoa particular shape for a given application. In this regard, thenon-conductive sheet 100 may be described as an elastic memory sheethaving a sheet width dimension and a sheet length dimension alongrespective axes A-A and B-B shown in FIGS. 3 and 4. Similarly, each ofthe first and second patterns 71, 81 have a corresponding, respectivepattern width dimension and a respective pattern length dimension alongrespective axes. In one example that is not limiting of this disclosure,the sheet width dimension and the respective pattern width dimensionsstretch and contract by an amount of 2 percent to 10 percent,simultaneously, in the presence of the deforming forces along acorresponding axis A-A or B-B. Similarly, the sheet length dimension andsaid respective pattern length dimensions stretch and contract by anamount of 2 percent to 10 percent, simultaneously in the presence of thedeforming forces along the other axis A-A or B-B. Deforming forces onthe sheet may include at least one of tensile forces, compressiveforces, shear forces, and combinations thereof, such as forces used forinstalling or molding the substrate 190 for placement on or within acorresponding vehicle component (e.g., around a steering wheel, along anA-pillar or B-pillar, in a seat, or even on an accessory such as aparking brake, a visor, a head rest, or a dash board accessory of thevehicle).

The conductive traces 122, 124A-C of the substrate 190 form respectivesensing circuits 8 and shielding circuits 7 on a single base sheet 100(FIG. 5). The non-conductive nature of the sheet 100 prevents shortcircuits through the sheet and controls both a sensing capacitance andparasitic capacitance levels in a sensing operation. In one embodiment,the conductive traces 122, 124A-C are formed by printing, preferably butnot exclusively screen printing, the conductive traces, and then eithercuring the conductive traces at a pre-defined temperature or letting theconductive traces dry on each side of the sheet before use. In thisregard, all of the conductive traces on the opposite sides of the sheetform a solidified derivative structure of a fluidic and printablecomposition, such as a conductive ink. In one embodiment, the solidifiedderivative structure is a stretchable conductive ink, such as a silverpolymer ink shown in FIG. 1.

As noted, the substrate 190 is used for electrical sensing systems in avehicle and may incorporate a base layer 100 in the form of anon-conductive sheet that is also flexible, conducive to formingmultiple shapes, and can be stretched for placement on or within avehicle component. The non-conductive sheet 100 may be a film thatsupports the conductive traces 122, 124A-C without allowing any shortcircuits through the sheets. The sheet may be a plastic film and may beselected from numerous polymeric materials including films selected frompolyethylene terephthalate (PET), polyethylene naphthalate (PEN),polyimide plastics (PI), and combinations thereof. Other sheets may bemore conducive to stretching as described above and be formed of aplastic film comprises a thermoplastic polyurethane film. The plasticfilm is impervious to a conductive ink used to form the conductivetraces. In other embodiments, the non-conductive sheet may be a fabric,including at least one of woven fabrics, non-woven fabrics, andcombinations thereof. For fabrics that would ordinarily absorb theconductive inks and cause bleed-through problems (and short circuitsbetween the opposite faces 110, 120), the fabric may include a surfacefinish that enables screen printing and is resistant to the fabricabsorbing a conductive ink used to form the respective traces. Toaccomplish a dual sided circuit on the substrate, fabric or a film has asufficient surface energy to promote adhesion of the conductive traces.

In another embodiment, a substrate for use in electrical sensing ofoccupants and other objects in a vehicle has a sensing circuit 8, 124A,124B, 124C and a shielding circuit 7, 122 on opposite faces 110, 120 ofthe same sheet 100. The sheet is a non-conductive base material having afirst face 110 and a second face 120 and respective conductive tracesadhered onto the first face and the second face. The base material andthe traces are both formed of flexible compositions with a mutualresilience allowing the base material and the conductive traces tostretch and contract in conjunction with one another and maintainelectrical continuity of the conductive traces in the presence ofdeforming forces upon the substrate. In this embodiment, the substratemay also include a first carbon polymer layer 140A connected to thefirst face 110 of the sheet 100 and a second carbon polymer layer 140Bconnected to the second face 120 of the sheet 100. In the example ofFIG. 1, the respective conductive traces include a first silver polymerconductive trace on the first face and a second silver polymerconductive trace on the second face. FIG. 1, as well as numerous otherfigures in this disclosure, show that one set of the conductive traces124A, 124B, 124C (i.e., the second silver polymer conductive trace) isformed into a plurality of zones of the conductive traces. The use ofdifferent zones for sensing circuits is discussed further below.

The substrates 190 used for sensing circuits 8, 124A-C and shieldingcircuits 7, 122 as discussed herein may be configured for manufacturingwith printing processes that form the conductive traces thereon. In amethod of forming the circuits, a first step includes applyingrespective fiducials to a first face 110 and a second face 120 of aflexible fabric, sheet, or film layer (base material 100) to guide aprinting process. Next, the sheet is held in place at a constant tensionand maintained in stable dimensions for printing a first conductivetrace 122 of a first pattern 71 on the first face 110 of the flexiblebase material. The method further includes printing a second conductivetrace 124 of a second pattern 81 on the second face 120 of the flexiblebase material, wherein the printing is completed according to aplacement of the fiducials. The first and second pattern can be entirelydistinct from one another as shown in FIGS. 3 and 4, or the patterns canbe similar or even identical so far as a general pattern is concerned.In one method, the fiducials are screen print fiducials and the printingis screen printing with a conductive ink. Prior to printing the secondconductive trace, a manufacturing method includes applying at least oneof the respective fiducials to the second face and screen printing thesecond conductive trace. Prior to applying the at least one of therespective fiducials, a step includes drying the first conductive traceand turning the flexible fabric to print on the second face. Therespective fiducials define the second conductive trace as a pluralityof zones for sensing different aspects of a vehicle occupant's positionor body parts at different regions along the substrate. In one optionalstep, the method further includes applying a carbon polymer to at leastone side of the flexible fabric.

In yet another embodiment, a substrate 190 used in capacitive sensingtechnologies within a vehicle includes a non-conductive base material100 having a first face 110 and a second face 120. Respective conductivetraces 122, 124A-C define respective patterns 71, 81 adhered onto thefirst face and the second face, wherein said patterns define a pluralityof redundant electrically conductive pathways across regions of thepatterns. The base material and the traces are both made of flexiblecompositions with a mutual resilience allowing the base material and theconductive traces to stretch and contract in conjunction with oneanother and maintain electrical continuity of the conductive traces inthe presence of deforming forces upon the substrate. A first carbonpolymer layer 140A is connected to the first face 110 of the basematerial 100, and a second carbon polymer layer 140B is connected to thesecond face 120 of the sheet. The carbon polymer layers extend over andbetween the conductive traces for additional redundancy in electricalconductivity. The carbon polymer layers 140A, 140B are configured asrespective protective coatings, but the carbon polymer layers also serveas capacitive plates on opposite sides of the base material ornon-conductive sheet or fabric. The carbon polymer material is depositedover the respective traces and into wells C1, C2, C3 and W1, W2 formedbetween the traces 122, 124A-C. The resulting carbon polymer plate,positioned over the sensing circuit, is conductive to an extent thatprovides a consistent electrical plate as part of a capacitive circuitcomponent formed between the sensing circuits 124A-C on the substrate190 and a human body part or other conductive object proximate theconductive capacitor plate formed by the carbon polymer later 140B. Inone non-limiting embodiment, the carbon polymer layer is about 0.015 mmthick. On the opposite side 110, the respective carbon polymer 140A, isa capacitor plate controlling the presence of parasitic capacitance orundesirable electromagnetic forces relative to an oppositely positionedmetal part, such as a steering wheel frame or seat construction. Thecarbon polymer layer is less conductive than the conductive traces butis still sufficiently conductive to increase the surface area of asensing circuit and a shielding circuit in which active electricalresponses are present.

As noted above, the conductive traces on opposite sides of the substratecan be connected to electrical circuits and used for capacitive sensingand shielding functions in the vehicle as part of occupant monitoring,safety systems, or accessory control systems in a vehicle. In somenon-limiting embodiments and only for example herein, a substrate 190having a sensing circuit and a shielding circuit thereon may be wrappedaround a steering wheel in a construction similar to that of FIGS. 2 and5. FIG. 5 illustrates a cross section of a steering wheel rim that couldinclude a substrate 190 as shown in FIG. 1. The steering wheelembodiment includes a frame 12, an over molded layer 14 around the frame12, and an optional heater mat layer 6 around the over molded layer 14.The substrate 190 described herein provides a shield circuit 7 formed ofthe respective conductive traces 122 on a first side 110 of anon-conductive sheet, fabric, or film 100 of a substrate 190. The shieldcircuit 7 could be formed of a printed conductive ink pattern that wouldface the steering wheel frame 12. A sensor circuit 8 is positioned on asecond side 120 of the same non-conductive sheet 100 opposite the shieldcircuit 7. The steering wheel may be completed with a skin 20 around thesensor circuit 8. The frame 12 is typically a magnesium alloy, aluminumalloy, steel, or a combination thereof, but it may be made of anothersuitable rigid material(s). The over molded layer 14 is formed from apolyurethane foam or thermoplastic elastomeric foam, for example. Theouter skin 20 is typically made of leather or vinyl, but could alsoinclude wood, carbon fiber, plastic, polyurethane foam, fabrics, or anyother suitable material. By keeping the shield circuit 7 directlyadjacent the sensor circuit 8, the distance fluctuation between the twocircuits is controlled by a known sheet thickness that does not varywidely because opportunities for thermal expansion and contraction areminimized. In addition, the distance between these layers is furtherminimized by the tension of the outer skin 20 squeezing substrate andother components of the steering wheel assembly together.

FIG. 6 illustrates a perspective view of the substrate 190 described assupporting a sensor circuit 8, shield circuit 7, alongside a heater mat6. Obviously in this application, the base material or sheet 100 must bemade of a fabric or plastic that maintains structural integrity in theface of heat provided to the steering wheel (e.g., a fabric instead of afilm for the base material 100) The sensor circuit 8 may include one ormore sensing zones, such as sensing zones 124 a, 124 b, 124 c, which aredesignated as zones 1-3 for example, and that are distinct and spacedapart from each other. In addition, the shield circuit 7 and the heatermat 6 may include one or more conductive zones, such as conductive zones54 a, 54 b, 54 c and 52 a, 52 b, 52 c, respectively, which correspond tothe sensing zones on the sensor mat and which allow for selective zoneshielding and heating.

An electronic control unit (ECU) 30, which is shown in FIG. 7, is inelectronic communication with the heater mat 6, the sensor circuit 8,the shield circuit 7, and one or more other vehicle systems (not shown).In particular, sensor return wires 34 a-34 c extend between the ECU 30and each sensing circuit 124 a-124 c, respectively, and conductive feedwires 56 a-56 c and 58 a-58 c extend between the ECU 30 and eachconductive loop 52 a-52 c and 54 a-54 c for the heater mat 6 and theshield circuit 7, respectively. The ECU 30 includes a processor 31 and apower source 32.

The processor 31 is configured for detecting input from a driver, suchas presence of a hand, adjacent each sensing loop 124 a-124 c. In oneimplementation, an electrical signal from one or more sensing loops 124a-124 c is communicated to the processor 31, and the processor 31determines if the signal indicates input from the driver. For example,the signal may be generated through capacitance-type sensing, and theprocessor 31 may compare the generated signal with a range of signalsthat indicates presence of the driver's hand or other parts of thedriver's body.

In addition to being configured to detect presence of a hand or otherparts of the driver's body, the sensing circuits 124 a, 124 b, 124 c andthe processor 31 may also be configured to detect various types of userinput in each respective sensing zone, such as a grip, swipe motion, tapmotion, etc., from signals received from the sensor mat. For example, byusing a multi-zone sensor mat with the sensing loops disposed inspecific areas, the sensor mat may be configured for detecting when no,one, or both hands are on the steering wheel and/or when a knee istouching the steering wheel. The embodiments are not limited to onlysensing a human, other animal or a given body part, but the substrate190 has appropriate circuits to sense any conductive object whether astatic, inanimate object that causes an electrical response in thecircuits of the substrate or a living dynamic animal or human.

Referring back to the example of FIG. 7, which is not limiting of thisdisclosure, the power source 32 is configured for selectively generatingan electrical current through one or more conductive loops 52 a-52 c ofthe heater mat 6 for heating at least a portion of the outer skin 20 anda voltage signal through one or more conductive loops 54 a-54 c (i.e.,the shielding circuit 7, 122) for shielding at least a portion of thesensor circuit 8, 124A-C from interference from the steering wheel frame12. The heating current is greater than a shielding current. Forexample, the heating current is around 4 to around 8 amperes, which issufficient for producing heat for heating the skin 20 of the steeringwheel, and the shielding current is less than about 200 microamperes,which is sufficient for shielding the sensor mat 8 from the steeringwheel frame 12, according to some implementations. In certainimplementations, for example, the shielding current may be between about9 to about 11 microamperes. In one particular implementation, theheating current may be about 7 amperes and the shielding current may bearound 10 microamperes. These electrical current values may be per zoneor per channel and are input into the ECU 30, according to certainimplementations.

In one implementation (not shown), the ECU 30 may include at least afirst circuit and a second circuit between the power source 32 and theconductive loops 52 a-52 c and 54 a-54 c, respectively. The firstcircuit receives the heating current, which is a simple, resistivevoltage current, to heat the area adjacent the conductive loops 52 a-52c. The second circuit receives the shielding current, which may be afrequency-specific signal, for example, to shield the area adjacent theconductive loops 54 a-54 c. The frequency-specific signal of the secondcircuit is configured for matching, as close as possible, thecapacitance voltage signal generated for the sensing mat.

The level of heating current, sensing voltage level or shielding voltagesignal to be generated by the power source 32 is controlled by theprocessor 31, according to one implementation. For example, in variousimplementations, the processor 31 may be configured to instruct thepower source 32 to generate the heating current in one or moreconductive loops 52 a-52 c in response to receiving input from a button,switch, or other suitable input mechanism disposed on the steering wheelor elsewhere in the vehicle. In another implementation, the processor 31may be configured for generating the heating current in response toreceiving input from one or more sensing loops 124 a-124 c. For example,in a particular implementation, the processor 31 may be furtherconfigured to instruct the power source 32 to generate the heatingcurrent for a particular conductive loop(s) 52 a-52 c that is adjacentthe particular sensing loop(s) 124 a-124 c that senses the presence ofthe driver's hand(s). This configuration allows the system to saveenergy by only heating those portions of the steering wheel rim forwhich the presence of the driver's hand is sensed. For example, if theprocessor 31 senses the presence of the driver's hand adjacent sensingcircuit 124 a, the processor 31 may generate the heating current throughthe conductive loop 52 a that is adjacent sensing loop 124 a to warm theportion of the steering wheel under the driver's hand.

In another implementation, or in addition to the implementationdescribed above, the processor 31 may be configured for instructing thepower source 32 to generate the heating current until the earlier of thesteering wheel reaching a preset temperature or receiving an overridesignal from another vehicle system indicating that sensing in one ormore zones takes priority over heating. In particular, the processor 31may receive a temperature signal from one or more temperature sensors inthe steering wheel and determine from the temperature signal whether thepreset temperature has been reached. For example, a typical heaterregulation range can be anywhere from about 30° C. to about 42° C. Thetemperature is typically detected using one or more thermistors, such asa negative temperature coefficient (NTC) type thermistor, according tocertain implementations. The thermistor provides feedback to theprocessor 31, and the processor 31 uses the temperature feedback toregulate the target temperature on the steering wheel.

In addition, the override signal may indicate to the processor 31 thatanother system should receive electrical resources that would otherwisebe allocated to the heater mat 6 for the heater function or that inputfrom the sensor mat 8 takes priority over heating.

In another implementation, or in addition to the implementationdescribed above, the processor 31 may be configured for instructing thepower source 32 to alternate generation of the heating current and theshielding voltage signal periodically, such as alternating every about10 to about 50 milliseconds. In other implementations, the period may bebetween about 10 to about 100 milliseconds. The period of alternationmay be set based on the speed of the processor 31, the outside or insidetemperature, or the preferences of the driver, for example. In addition,on board temperature monitoring may affect the timing, such as toprevent overheating of the controller itself. Or, if a specific faultcondition is detected and the ECU 30 needs to prioritize managing thatfault condition, the timing may be affected.

In the alternative implementation shown in FIG. 8, a first power source62A is provided for generating a heating current for the heater mat 6and a second power source 62B is provided for generating a shieldingvoltage signal for the shield circuit 7. The first 62A and second powersources 62B are shown in FIG. 8 as being within two separate ECUs 60A,60B, respectively, but, alternatively, these may be included in one ECU60, as shown in FIG. 9. These implementations allow the system toprovide for continuous shielding and heating when desired, for example.In addition, ECU 60A or 60 may include a first circuit for receiving theheating current from power source 62A, which is a simple, resistivevoltage current, to heat the area adjacent the conductive loops ofheater mat 6. And, ECU 60B or 60 may include a second circuit forreceiving the shielding voltage signal from power source 62B, which maybe a frequency-specific signal, for example, to shield the area adjacentthe conductive loops of shield mat 7.

Furthermore, in sensor circuits having multiple zones, signals carriedby sensor return wires associated with each sensing zone may generatenoise in the sensing loops or sensor return wires associated withadjacent zones when the wires are too close to each other. This noisedecreases the ability of the sensor mat to detect presence of a handadjacent one or more sensing zones. In addition, cross talk from asensor return wire from one zone that crosses over another zone mayresult in unintended detection from another zone. Accordingly, variousimplementations described herein provide for shielding around at least aportion of the sensor return wires that may be disposed adjacent anothersensing zone or sensor return wire to isolate the signal(s) carried bythe sensor return wire(s).

Furthermore, biometric type sensors may be disposed in the vehicle towork in conjunction with hand sensing through the steering wheel usingnon-biometric type sensors. These biometric sensors may be disposed onthe steering wheel or elsewhere in the vehicle. Examples of thesebiometric type sensors include retina detection, heart rate monitoring,arousal state monitoring, and driver detection (e.g., in a vehicleseat).

As shown in FIG. 10, the ECU 30 is in electronic communication with theheater mat 16, the sensor circuit 18, and one or more other vehiclesystems (not shown). In particular, the sensor return wires 34 a-34 cextend between the ECU 30 and each sensing zone and conductive feedwires 36 a-36 c from the heater mat 16 extend between the ECU 30 andeach portion of a heater mat used with the substrate of this disclosure.

FIG. 11 illustrates a schematic top view of the sensor circuit 18showing the path of each of three sensor return wires 34 a, 34 b, 34 cextending from their respective sensing circuit zones 124 a, 124 b, 124c. As shown, the sensor return wire 34 a extends over a portion ofsensing loop 124 b, which may be a source for interference for sensingloop 124 b. To isolate the signal carried by the sensor return wiresfrom each other while allowing for efficient routing of wires along thesensor mat 18, one or more of the sensor return wires 34 a-34 cextending between the ECU 30 and the sensing loops 124 a-124 c mayinclude shielding around at least a portion of the sensor return wire 34a-34 c.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art. Methods and materials similar or equivalent to those describedherein can be used in the practice or testing of the present disclosure.As used in the specification, and in the appended claims, the singularforms “a,” “an,” “the” include plural referents unless the contextclearly dictates otherwise. The term “comprising” and variations thereofas used herein is used synonymously with the term “including” andvariations thereof and are open, non-limiting terms. Whileimplementations will be described for steering wheel hand detectionsystems, it will become evident to those skilled in the art that theimplementations are not limited thereto.

As utilized herein, the terms “approximately,” “about,” “substantially”,and similar terms are intended to have a broad meaning in harmony withthe common and accepted usage by those of ordinary skill in the art towhich the subject matter of this disclosure pertains. It should beunderstood by those of skill in the art who review this disclosure thatthese terms are intended to allow a description of certain featuresdescribed and claimed without restricting the scope of these features tothe precise numerical ranges provided. Accordingly, these terms shouldbe interpreted as indicating that insubstantial or inconsequentialmodifications or alterations of the subject matter described and claimedare considered to be within the scope of the invention as recited in theappended claims.

It should be noted that the term “exemplary” as used herein to describevarious embodiments is intended to indicate that such embodiments arepossible examples, representations, and/or illustrations of possibleembodiments (and such term is not intended to connote that suchembodiments are necessarily extraordinary or superlative examples).

The terms “coupled,” “connected,” and the like as used herein mean thejoining of two members directly or indirectly to one another. Suchjoining may be stationary (e.g., permanent) or moveable (e.g., removableor releasable). Such joining may be achieved with the two members or thetwo members and any additional intermediate members being integrallyformed as a single unitary body with one another or with the two membersor the two members and any additional intermediate members beingattached to one another.

References herein to the positions of elements (e.g., “top,” “bottom,”“above,” “below,” etc.) are merely used to describe the orientation ofvarious elements in the FIGURES. It should be noted that the orientationof various elements may differ according to other exemplary embodiments,and that such variations are intended to be encompassed by the presentdisclosure.

It is important to note that the construction and arrangement of thesensing system for a steering wheel as shown in the various exemplaryembodiments is illustrative only. Although only a few embodiments havebeen described in detail in this disclosure, those skilled in the artwho review this disclosure will readily appreciate that manymodifications are possible (e.g., variations in sizes, dimensions,structures, shapes and proportions of the various elements, values ofparameters, mounting or layering arrangements, use of materials, colors,orientations, etc.) without materially departing from the novelteachings and advantages of the subject matter described herein. Forexample, elements shown as integrally formed may be constructed ofmultiple parts or elements, the position of elements may be reversed orotherwise varied, and the nature or number of discrete elements orpositions may be altered or varied. The order or sequence of any processor method steps may be varied or re-sequenced according to alternativeembodiments. Other substitutions, modifications, changes and omissionsmay also be made in the design, operating conditions and arrangement ofthe various exemplary embodiments without departing from the scope ofthe present embodiments.

The figures utilize an exemplary computing environment in which exampleembodiments and aspects may be implemented. The computing deviceenvironment is only one example of a suitable computing environment andis not intended to suggest any limitation as to the scope of use orfunctionality.

Numerous other general purpose or special purpose computing devicesenvironments or configurations may be used. Examples of well-knowncomputing devices, environments, and/or configurations that may besuitable for use include, but are not limited to, personal computers,server computers, handheld or laptop devices, multiprocessor systems,microprocessor-based systems, network personal computers (PCs),minicomputers, mainframe computers, embedded systems, distributedcomputing environments that include any of the above systems or devices,and the like.

Computer-executable instructions, such as program modules, beingexecuted by a computer may be used. Generally, program modules includeroutines, programs, objects, components, data structures, etc. thatperform particular tasks or implement particular abstract data types.Distributed computing environments may be used where tasks are performedby remote processing devices that are linked through a communicationsnetwork or other data transmission medium. In a distributed computingenvironment, program modules and other data may be located in both localand remote computer storage media including memory storage devices.

In its most basic configuration, a computing device typically includesat least one processing unit and memory. Depending on the exactconfiguration and type of computing device, memory may be volatile (suchas random access memory (RAM)), non-volatile (such as read-only memory(ROM), flash memory, etc.), or some combination of the two.

Computing devices may have additional features/functionality. Forexample, computing device may include additional storage (removableand/or non-removable) including, but not limited to, magnetic or opticaldisks or tape. Such additional storage is illustrated in FIG. 2 byremovable storage and non-removable storage.

Computing device typically includes a variety of computer readablemedia. Computer readable media can be any available media that can beaccessed by the device and includes both volatile and non-volatilemedia, removable and non-removable media.

Computer storage media include volatile and non-volatile, and removableand non-removable media implemented in any method or technology forstorage of information such as computer readable instructions, datastructures, program modules or other data. Memory, removable storage,and non-removable storage are all examples of computer storage media.Computer storage media include, but are not limited to, RAM, ROM,electrically erasable program read-only memory (EEPROM), flash memory orother memory technology, CD-ROM, digital versatile disks (DVD) or otheroptical storage, magnetic cassettes, magnetic tape, magnetic diskstorage or other magnetic storage devices, or any other medium which canbe used to store the desired information and which can be accessed bycomputing device. Any such computer storage media may be part ofcomputing device.

Computing device 200 may contain communication connection(s) that allowthe device to communicate with other devices. Computing device may alsohave input device(s) such as a keyboard, mouse, pen, voice input device,touch input device, etc. Output device(s) such as a display, speakers,printer, etc. may also be included. All these devices are well known inthe art and need not be discussed at length here.

It should be understood that the various techniques described herein maybe implemented in connection with hardware components or softwarecomponents or, where appropriate, with a combination of both.Illustrative types of hardware components that can be used includeField-programmable Gate Arrays (FPGAs), Application-specific IntegratedCircuits (ASICs), Application-specific Standard Products (ASSPs),System-on-a-chip systems (SOCs), Complex Programmable Logic Devices(CPLDs), etc. The methods and apparatus of the presently disclosedsubject matter, or certain aspects or portions thereof, may take theform of program code (i.e., instructions) embodied in tangible media,such as CD-ROMs, hard drives, or any other machine-readable storagemedium where, when the program code is loaded into and executed by amachine, such as a computer, the machine becomes an apparatus forpracticing the presently disclosed subject matter.

FIG. 12 illustrates an example of a computer environment in which theabove described electronic control unit operates. In general, the ECU30, designated to control sensing and shielding operations as describedabove, processes signals, whether power signals or data signals,received from and/or provided to the shield circuit 7, the sensorcircuit 8, and a heater mat 6. With the appropriate processor 202 andmemory 204, the ECU 30 can be configured with computer implementedsoftware to ensure that the circuits in the overall shielding, sensing,and heating systems of this disclosure operate for the purposesdescribed above. In one sense, the ECU 30 may be local to the substrate190 of this disclosure, and in certain non-limiting embodiments, mayinclude a somewhat basic configuration 206 that is tailored to controlonly the sensing, shielding, and heating circuits in a substrateinstallation. This local ECU 30 may also be connected to a more globalvehicle control system that implements a plurality of vehicle systemsand accessories with more powerful hardware configurations, generallydesignated as a computerized vehicle data management system 200. It isnotable that a vehicle-wide data management system 200 will likelyinclude system memory and processors, but will also incorporate moresophisticated kinds of memory devices 208, 210, multiple I/O connections212, 214, and a network interface controller 216 for diverse datacommunications throughout the vehicle. In this regard, the variouscomponents of computerized systems utilized for sensing technologyherein are selected to transfer data or even power signals betweensource devices and recipient devices according to variousimplementations that tailored to the use at hand. In particular, theembodiments of this disclosure may utilize any kind of computeroperations capable of network connection, including accessories such ashuman machine interface systems (e.g., touch pad(s), touch sensitiveareas on a display, and/or switches for interfacing with one or morecomponents on a data communications network handling occupant sensingand corresponding user communications).

Although exemplary implementations may refer to utilizing aspects of thepresently disclosed subject matter in the context of one or morestand-alone computer systems, the subject matter is not so limited, butrather may be implemented in connection with any computing environment,such as a network or distributed computing environment. Still further,aspects of the presently disclosed subject matter may be implemented inor across a plurality of processing chips or devices, and storage maysimilarly be effected across a plurality of devices.

Although the subject matter has been described in language specific tostructural features and/or methodological acts, it is to be understoodthat the subject matter defined in the appended claims is notnecessarily limited to the specific features or acts described above.Rather, the specific features and acts described above are disclosed asexample forms of implementing the claims.

The invention claimed is:
 1. A substrate comprising: a non-conductivesheet having a first face and a second face; respective conductivetraces adhered to the first face and the second face, wherein said sheetand said traces each comprise flexible compositions with mutualresilience to stretch and contract in conjunction with one another, saidresilience maintaining structural continuity of the conductive traces inthe presence of deforming forces upon the sheet.
 2. A substrateaccording to claim 1, wherein said sheet and said conductive traces areconfigured to withstand deforming forces that stretch a dimension ofsaid sheet in any direction by an amount between 2 percent and 10percent.
 3. A substrate according to claim 1, wherein said conductivetraces define a first pattern on said first face and a second pattern onsaid second face, wherein said sheet comprises an elastic memory sheethaving a sheet width dimension and a sheet length dimension; whereineach of said first and second patterns comprise a respective patternwidth dimension and a respective pattern length dimension; and whereinsaid sheet width dimension and said respective pattern width dimensionsstretch and contract by an amount of 2 percent to 10 percent,simultaneously, in the presence of the deforming forces.
 4. A substrateaccording to claim 3, wherein said sheet length dimension and saidrespective pattern length dimensions stretch and contract by an amountof 2 percent to 10 percent, simultaneously in the presence of thedeforming forces.
 5. A substrate according to claim 1, wherein saiddeforming forces comprise at least one of tensile forces, compressiveforces, shear forces, and combinations thereof.
 6. A substrate accordingto claim 1, wherein said conductive traces comprise a solidifiedderivative structure of a fluidic and printable composition.
 7. Asubstrate according to claim 6, wherein said fluidic and printablecomposition is a conductive ink.
 8. A substrate according to claim 6,wherein said solidified derivative structure is a stretchable conductiveink.
 9. A substrate according to claim 1, wherein said non-conductivesheet comprises a film.
 10. A substrate according to claim 1, whereinsaid non-conductive sheet comprises a plastic film.
 11. A substrateaccording to claim 10, wherein said plastic film is selected from thegroup consisting of PET, PEN, PI, and combinations thereof.
 12. Asubstrate according to claim 10, wherein said plastic film comprises athermoplastic polyurethane film.
 13. A substrate according to claim 10,wherein said plastic film is impervious to a conductive ink used to formthe conductive traces.
 14. A substrate according to claim 1, whereinsaid non-conductive sheet is a fabric.
 15. A substrate according toclaim 14, wherein said fabric comprises at least one of woven fabrics,non-woven fabrics, and combinations thereof.
 16. A substrate accordingto claim 14, wherein said fabric has a surface finish that enablesscreen printing.
 17. A substrate according to claim 16, wherein saidsurface finish is resistant to the fabric absorbing a conductive inkused to form the respective traces.
 18. A substrate comprising: anon-conductive base sheet having a first face and a second face,respective conductive traces adhered directly onto the first face andthe second face, wherein said base sheet and said traces each compriseflexible compositions with a mutual resilience allowing the base sheetand the conductive traces to stretch and contract in conjunction withone another and maintain electrical continuity of the conductive tracesin the presence of deforming forces upon the substrate; a first carbonpolymer layer connected to the first face of substrate; and a secondcarbon polymer layer connected to the second face of the substrate. 19.A substrate according to claim 18, wherein said respective conductivetraces comprise a first silver polymer conductive trace on said firstface and a second silver polymer conductive trace on said second face.20. A substrate comprising: a single non-conductive base layer having afirst face and a second face; respective conductive traces definingrespective patterns adhered onto the first face and the second face,wherein said patterns define a plurality of redundant electricallyconductive pathways across regions of the patterns; wherein said baselayer and said traces each comprise flexible compositions with a mutualresilience allowing the base layer and the conductive traces to stretchand contract in conjunction with one another and maintain electricalcontinuity of the conductive traces in the presence of deforming forcesupon the substrate; a first carbon polymer layer connected to the firstface of substrate; and a second carbon polymer layer connected to thesecond face of the substrate, wherein said carbon polymer layers extendover and between said conductive traces for additional redundancy inelectrical conductivity.